This invention relates generally to liquid crystal display devices and particularly to a pixel electrode structure for such devices.
Liquid crystal display devices are composed of a matrix of pixels arranged horizontally in rows and vertically in columns. The individual liquid crystals are defined by transparent electrodes which determine the configuration of the liquid crystal cell. In active matrix liquid crystal displays, each liquid crystal cell is associated with a thin film transistor (TFT), or other solid state switching device, which serves as a switch to selectively turn the liquid crystals on and off. Select lines run horizontally between the rows of pixel electrodes and the gates of the TFTs are coupled to the select lines. Accordingly, a complete horizontal row of pixel electrodes is simultaneously "turned on" upon the selection of a particular select line. Data lines run vertically between the columns of pixel electrodes and are used to apply the display producing data signals to the pixel electrodes of a particular column. However only the pixels which are associated with energized TFTs receive the data signals. The display is therefore produced one line at a time. Typically, the source of the TFT is electrically coupled to the drive line and the drain of the TFT is coupled to the pixel electrode.
In the prior art, space for the TFTs is provided by removing a corner of the pixel electrodes and fabricating the TFTs in the vacated areas. This is disadvantageous because the pixel electrodes are transparent to light while the TFTs are not. Accordingly, the corner of the pixel electrode which is removed to provide space for the TFTs is no longer transparent to light and the amount of light passing through the electrode is decreased by the same percentage as the percentage of decrease in the area of the electrode.
For this reason there is a need for a liquid crystal pixel electrode and TFT structure which maximizes the area for light transmission in a liquid crystal display. The present invention fulfills this need.